1. Field of the Invention
The present invention relates to a sorter-finisher, specifically, a sorter-finisher wherein sheets discharged from an image forming apparatus such as an electro-photographic copying machine are distributed among a plurality of bins equipped for a sorter unit, and thereafter the sheets are taken out thereof and transported to a finisher unit to be subjected to finishing operation such as stapling operation.
2. Description of Related Art
Recently, responding to the increasing demand for automatic paper handling systems for copying machines, and a sorting system for sorting and grouping copied sheets have been developed and commercialized in various types. The users of the copying machines are requiring a sorter-finisher capable of automatically binding and stacking sheet which have been distributed in the sorting system, and this type of sorter-finisher has been already commercialized for some of large-sized copying machine.
When combining a finisher with a sorter, a paper take-out position where sheets stored in each bin are taken out thereof should be iinstalled, In providing a finisher for a sorter which has a plurality of bins arranged one upon another, suppose that the paper take-out position is arranged under the bins. In this type of sorter-finisher, when more bins are demand, the additional bins have to be put above the formers, thereby making the whole apparatus larger. Further, the size of the finisher unit depends on the maximum sheet size which can be subjected to the finishing operation. When the paper take-out position is arranged under the bins, the finisher unit should be arranged under the bins, too. Accordingly, the arrangement makes the whole apparatus larger.
Also, when providing a finisher for a sorter which has a plurality of bins arranged one upon another, in order to take sheets out of the bins, conventionally, a pair of nippers or a pair of rollers equipped for an arm at the end enters each bin to nip sheets therein at the edge. In this case, in order to prevent the pair of rollers or nippers from coming into contact with the upper and the lower bins, the intervals among the bins should be widened. Accordingly, a cam with a spiral groove whose pitch is partly wide is in general use, and the intervals among the bins are widened in response to the rotation of the cam according to the step of the paper take-out operation. However, it costs a lot to make a spiral cam.
An apparatus wherein a pair of rollers provided for an arm at the end enters each bin to nip sheets in the bin at the end portion and take tha sheets out thereof is disclosed by U.S. Pat. No. 4,811,048. However, it is not enough to just nip sheets at the end portion by a pair of rollers. When the end portion of the sheets is curled, the pair of rollers may push the sheets on the bin to reverse, resulting in a failure in nipping.
In another point, when a finisher is provided for a sorter, two paper paths, one of which leads paper from an image forming apparatus to a sorter, and the other of which leads paper from the sorter to a finisher, are necessary. As a result, here comes the problem that the whole apparatus becomes larger.